What balance problems arise by allowing grappling as an option for an Opportunity Attack?

In our last session (with me as the DM), a creature was surrounded by the party and was trying to flee. She cast Levitate on herself to try to float up and get away. As she was going up and thereby out of reach of several party members, they each got an Opportunity Attack against her. Several of them wanted to use this opportunity attack to try to grapple, holding on to her to keep her from getting away, rather than a more traditional melee attack. I wasn’t sure whether this was an allowed way to take an Opportunity Attack, but the scene of her floating up with one of the player characters grabbing onto her legs as she went up was pretty neat, and I figured via Rule of Cool that I should just allow it. And it did lead to a really fun encounter, with the character dangling off the legs of this creature in midair trying to slap some manacles on her to prevent further spellcasting.

Now, after the session, I figured I’d look up the actual rules, and sure enough by the book Opportunity Attacks only allow for a melee attack, not a grapple. So I guess my question is, what issues might I encounter if I maintain this precedent of allowing a more generous set of actions as Opportunity Attacks? It sure seems that trying to tackle or trip somebody as they run past you could make for some fun scenes, and it feels more “realistic” in some sense than only allowing for a melee attack.

I’m a relatively novice DM, and am thus hesitant to go very far outside of the standard rules.

If I just allow for this — substitute in a Grapple for a melee attack during an Opportunity Attack — will this create balance problems?

How do the War Caster feat and the Enemies Abound spell interact when an opportunity attack is provoked?

The enemies abound spell states:

[…] If an enemy provokes an opportunity attack from the affected creature, the creature must make that attack if it is able to […]

Xanathar’s Guide to Everything (page 155)

And the War Caster feat states:

[…] When a hostile creature’s movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making an opportunity attack […]

Player’s Handbook (page 170)

Note that a spell cast using War Caster is not considered an opportunity attack

I’m now unsure what happens when somebody is under the enemies abound spell but also has the War Caster feat and an opportunity attack is provoked. Does War Caster allow them to cast a spell or does the phrasing of enemies abound (especially “that attack”) require them to make the opportunity attack?

Can we do “Hooves” attacks of opportunity?

The rulebook says that an attack of opportunity can be done on a foe leaving your reach area without disengaging. My thought is kind of reminiscent of the old wording “leaving a threatened area”, but anyways, here it is :

The “hooves” attack action description is as follows :

Hooves. Melee Weapon Attack: +5 to hit, reach 5 ft. one prone creature. Hit: 8 (2d4 + 3) bludgeoning damage.

(emphasis added; quote slightly modified for clarity)

Technically, could the hooves attack range be considered 5ft-ground, causing a standing-up character withing 5ft of an Elk’s hooves to trigger an attack of opportunity?


Note: This question is not a duplicate. It is specific to the Hooves attack which has very limited usage. The target needs to be proned and within 5 feet. This question is not about “how to perform an attack of opportunity”, but rather IF one can be performed with a hooves attack under certain conditions.

Deserialization Opportunity?

I have minimal experience exploiting deserialization vulnerabilities and I am working on and I have identified the following URL endpoint. This is it URL Decoded:

/Account/Register?Count=0&Keys=System.Collections.Generic.Dictionary`2+KeyCollection[System.String,System.Object]&Values=System.Collections.Generic.Dictionary`2+ValueCollection[System.String,System.Object] 

I’d appreciate some help explaining if it’s exploitable, and if so, how so I can prove impact to the client. Thank you.

Does the extra movement you get from the Travel Devotion Feat provoke attacks of opportunity?

If you employ the domain feat Travel Devotion (Complete Champion, p. 62) you can

Once per day as a swift action, (…) activate this ability to move up to your speed as a swift action each round.

The benefit granted by a domain feat usually is a spell-like ability (Complete Champion, p. 52). Since it is also a swift action it should be treated as a quickened spell-like ability, which according to the Rules Compendium (actions in combat, p. 8) does not provoke attacks of opportunity.

So my question is: Does this mean that the extra movement you get from this feat does not provoke attacks of opportunity?

Or is it just the activation of this ability which does not provoke attacks of opportunity – and the movement still does?

(I know that this feat has already been discussed quite a bit, but I haven´t found anything about this particular detail.)

Can you Attack of Opportunity yourself?

As far as I’m aware, you do threaten your square:

Most creatures of Medium or smaller size have a reach of only 5 feet. This means that they can make melee attacks only against creatures up to 5 feet (1 square) away.

If a Tiny creature is in your square, I’m used to being able to AoO that, as well.

For movement, it specifies that it’s threatening opponents that can take AoOs:

Moving out of a threatened square usually provokes attacks of opportunity from threatening opponents.

But most things simply say that an action provokes attacks of opportunity, and doesn’t clarify who is allowed to take them.

It may seem silly to ask if you can AoO yourself, but in certain builds it can actually be useful. Is there any RAW clarification on whether you’re allowed to take AoOs against yourself when you provoke?

How to hide without triggering opportunity attacks?

All halflings have the Halfling Nimbleness feature:

You can move through the space of any creature that is of a size larger than yours.

Lightfoot Halflings have the Naturally Stealthy ability:

You can attempt to hide even when you are obscured only by a creature that is at least one size larger than you.

Halflings are sized small, while Dragonborn, for instance, are medium.

A rogue has a Cunning Action:

You can take a bonus action on each of your turns in combat. This action can be used only to take the Dash, Disengage, or Hide action.

And our group has been playing with a Barbarian Dragonborn and the Lightfoot Halfling Rogue. In combat, let’s say, facing a single boss, the rogue usually hits and hides behind the Dragonborn (moving through him). A stealth check is rolled against the boss’s perception, and if the boss wins, he can go around the barbarian and hit the rogue. He does not trigger attacks of opportunity because he is not leaving the barbarian’s melee range.

However, for the rogue to go behind the dragonborn, he should trigger an opportunity attack from the boss, right? Or can the hide action include this 5 feet move to hide behind the dragonborn? Or does the nimbleness feature prevent attacks of opportunity, since the rogue can simply stand in the dragonborn’s space, only behind him? Does standing in the same space as a bigger creature prevent attacks against you because the creature shields you?

In terms of RP and realism, we’ve been describing this as such: the halfling is hiding in the back of the barbarian, pops out to strike, and hides back there. The idea here is to have the rogue safely out of harm’s way (dumb enemies won’t understand where he is, others will attack with disadvantage, and others will actually have to move to him him (unless they’re grappled).

War Caster, a whip and a dagger, and provoking Opportunity Attacks

This related question gives an answer about provoking opportunity attacks when wielding a dagger and a whip.

I am interested how this interacts with the feat War Caster (5e PHB p170):

When a hostile creature’s movement provokes an opportunity attack from you, you can use your reaction to cast a spell at the creature, rather than making the opportunity attack.

The reason is that the reach property of the whip is only valid if the weapon itself is used for the opportunity attack.

Do I get an opportunity attack with a spell when a creature leaves a square

  • adjacent from me (i.e. leaves dagger reach)?
  • 5ft away from me (i.e. leaves whip reach)?

Please give an answer according to the RAW, and specifically mention either Mearls or Crawford’s interpretation as basis, or answer for both.

Do opportunity attacks trigger booming blade? [duplicate]

This question already has an answer here:

  • Does Booming Blade trigger only when the creature moves locations? 1 answer

There have been some similar questions, such as here, but I was wondering if an opportunity attack triggers booming blade, for example (I will use mine) a dwarven cleric (he used magic initiate to get booming blade) hit a bugbear, and moved away. Would the bugbear take the booming blade effect damage when it does the opportunity attack?

Also, would you use strength as a modifier to hit with the melee weapon, or charisma since the melee attack is part of the spell? Thanks for your help!